1. Field of the Invention
The present invention relates generally to medical systems and methods. More particularly, the invention relates to methods for treating fibroids and other tissue masses in a potential space between the tissue mass and surrounding tissue.
Treatment of the female reproductive tract and other conditions of dysfunctional uterine bleeding and fibroids remain unmet clinical needs. Fibroids are benign tumors of the uterine myometria (muscle) and are the most common tumor of the female pelvis. Fibroid tumors affect up to 30% of women of childbearing age and can cause significant symptoms such as discomfort, pelvic pain, mennorhagia, pressure, anemia, compression, infertility and miscarriage. Fibroids may be located in the myometrium (intramural), adjacent to the endometrium (submucosal) or in the outer layer of the uterus (subserosal). Most commonly fibroids are a smooth muscle overgrowth that arise intramurally and can grow to be several centimeters in diameter.
Uterine fibroids are surrounded by a tissue interface referred to as a pseudo-capsule. The pseudo-capsule will usually provide a clear tissue plane between the fibroid and the surrounding tissue (myometrium), which potential space is often referred to as the peri-capsular space. At times, the fibroid may be mobile within this space.
Current treatments for fibroids include both pharmacological therapies and surgical interventions. Pharmacological treatment includes the administration of medications such as NSAIDS, estrogen-progesterone combinations, and GnRH analogues. All medications are relatively ineffective and are palliative rather than curative. Hysterectomy (surgical removal of the uterus) is another common treatment for fibroids. While effective, hysterectomy has many undesirable side effects such as loss of fertility, open surgery, sexual dysfunction and long recovery time. There is also significant morbidity (sepsis, hemorrhage, peritonitis, bowel and bladder injury), mortality and cost associated with hysterectomy. Surgical myomectomy, in which fibroids are removed, is an open surgical procedure requiring laparotomy and general anesthesia. Often these procedures are long with significant blood loss and can only remove a portion of the culprit tissue.
To overcome at least some of the problems associated with open surgical procedures, laparoscopic myomectomy was pioneered in the early 1990's. However, laparoscopic myomectomy remains technically challenging, requiring laparoscopic suturing which limits its performance to only the most skilled of laparoscopic gynecologists. Other minimally invasive treatments for uterine fibroids include hysteroscopy, uterine artery ablation, endometrial ablation, and myolysis.
Hysteroscopy is the process by which a thin fiber optic camera is used to image inside the uterus and an attachment may be used to destroy tissue. Hysteroscopic resection is a surgical technique that uses a variety of devices (loops, roller balls, bipolar electrodes) to ablate or resect uterine tissue. The uterus needs to be filled with fluid for better viewing and thus has potential side effects of fluid overload. Hysteroscopic ablation is limited by its visualization technique and is thus only appropriate for those fibroids that are submucosal and/or protrude into the uterine cavity.
Uterine artery embolization was introduced in the early 1990's and is performed through a groin incision by injecting small particles into the uterine artery to selectively block the blood supply to fibroids. Complications include pelvic infection, premature menopause and severe pelvic pain. In addition, long term MRI data suggest that incomplete fibroid infarction may result in regrowth of infarcted fibroid tissue and symptomatic recurrence.
Endometrial ablation is primarily a procedure for dysfunctional (or abnormal) uterine bleeding and may be used at times for fibroids. Endometrial ablation relies on various energy sources such as cryo energy, microwave energy and radiofrequency energy. Endometrial ablation destroys the endometrial tissue lining the uterus but does not specifically treat fibroids. This technique is also not for women who desire future childbearing. Endometrial ablation remains an excellent therapy for dysfunctional uterine bleeding but is limited in its ability to treat fibroids.
Myolysis was first performed in the 1980's using lasers or RF energy to coagulate tissue, denature proteins and necrose myometrium with laparoscopic visualization. Needle myolysis can use a laparoscopic or open surgical technique to introduce one or more needles into a uterine fibroid under endoscopic or direct visual control. The needle(s) can then be used to deliver energy, cryogenic fluids, or other treatment agents in order to coagulate a significant volume of the fibroid or other tumor to cause substantial shrinkage. Laparoscopic myolysis can be an alternative to myomectomy, as the fibroids are ablated and then undergo coagulative necrosis resulting in a dramatic decrease in size and lessening of symptoms. As with all laparoscopic techniques, myolysis treatment is limited to subserosal fibroids which can be laparoscopically visualized.
As an improvement over all of the above-described techniques, it has recently been proposed in co-pending application Ser. No. 11/409,496, assigned to the assignee of the present application, to treat uterine fibroids by penetrating a needle into the fibroid under ultrasonic imaging and delivering radiofrequency energy to the fibroid to ablate the fibroid tissue. Although this protocol has proven to be highly effective in many cases, some uterine fibroids are difficult to penetrate with needle electrodes due to fibroid tissue mobility within the myometrium where the needles will deflect from the fibroid tissue. Additionally, direct heating and ablation of the fibroid can in certain instances thermally fix the fibroid within the surrounding tissue, inhibiting the desired complete removal of the fibroid.
For these reasons it would be desirable to provide alternative methods for treating and shrinking or removing uterine fibroids and other tissue masses. It would be particularly desirable if such methods were able to treat uterine fibroids which are resistant to needle penetration or otherwise difficult to penetrate and to reduce or eliminate the chance of thermally fixing the fibroid within the surrounding uterine tissue. At least some of these objectives will be met by the inventions described below.
2. Description of the Background Art
US 2005/0107781 describes a bipolar fibroid ablation device having a first tissue penetrating array that is positioned on a remote side of the fibroid and a second non-penetrating array positioned on a near side of the fibroid. U.S. Pat. No. 5,979,453 describes a needle myolysis apparatus for directing radiofrequency current to a blood vessel supplying blood to a fibroid. U.S. Pat. No. 5,456,689 describes a device for resection of the uterine wall under ultrasound imaging.
The following commonly owned applications also relate to uterine fibroid treatment: Ser. No. 11/271,151, filed on Nov. 5, 2005; Ser. No. 11/347,018, filed Feb. 2, 2006; and Ser. No. 11/409,496, filed Apr. 20, 2006. The full disclosures of each of these copending applications are incorporated herein by reference.